Audio grip force and disconnect indicator and method



Aug. 12, 1958 o. J. STODDARD 2,847,653

AUDIO GRIP FORCE AND DISCONNECT INDICATOR AND METHOD Filed Aug. 8, 1955 2 Sheets-Sheet 1 IN VEN TOR.

oeeav 0.1 57000420 b zfzwv HTTO'QNEP' 1IIIIIII Aug. 12, 1958 Filed Aug. 8, 1955 2,847,663? AUDIO GRIP'FORCE 'AND'DISCONNECTI INDICATOR ANDMETHOD OrrenvJ: stoddardgah linneapolis', Minn.) assignor to General Mills lnct, acorporation' of Delaware Application August s,119ss;se'n'a'l No. 526,899 r 14 Claims. (Cli=340--282)*' Thi's invention relates in general to signaling systems and pertains more particularly to} an audio grip; force indicator and method for signifying to an operatorthe degree or magnitude of pressure being-applied to an object held between two relatively. 'movable clamping members;

The instant inventionlwill .find especial utilityin. remote control handling units such" as that disclosed in the application ofCharles'HQBergslandet-al., UQ'SI Serial 456,226, filed September 15, 1954. In handling radioactivemate'rials, a procedure contemplated in the above alluded toBergsland application, it is frequently necessaryto'manipulate frangible or fragile 'articles'from a remote, safevantage point, and such action demands-the utm'ostcare, lest the article's inadvertently become broken with a consequent heavy, loss, in "many instances, of time and money.- Scnsitivity ofcontrol is'not enough,for theoperator must also beconstantly warned of theforc'e being jjmechanically, applied to breakable articles so that he may alw'aysexercise the proper'degr'ee' of control over the equipment.

Since the operator'ha's no feel over the worhbeing handlei ther'e being a total absence of 'person'al contact, resorthas been made to visual indicators. However, these visual indicators have beengrossly inadequate, mainly due to the fact that the operators attention must be devoted to the watching of whatth'e equipment'is do'iri'gwithout'having to' shift his gaze to some instrument not always precisely in his line 'of sight. In order to obviate the 'foregoingdifiiculty encountered with visual indicators, an object of the present inventionfis to provide an "audible force indicator that will be" practical, reliable and satisfactory in its operation.

Rather broadly, the invention has for an aim the audible indication of the degreeiof forcebeing applie'd'toa pair of clampingljaws by producing a tonal pitch variable in accordance with such'force and providing a ready comparison of 'such'pitch'witha"given or reference pitch. More"specifically, the invention has for a feature the alternating of the reference pitch 'with the variable one. By accomplishing such alternations in a rapidly successivefashionor cycle, theoperator' has no time in'which to lose"'the' reference pitch; Thus, the operator is constantly presented with 'a basisupon which'he can predicate gripping force'changes, increasing or moderatingthemas circurnstances'dictate: In this way even relatively"tone deaf individuals are enabled to" operate properly" handling apparatusfiequipped with indicating means constructed in-accordance with the teachings of the instant invention; 'Ihbsef'endowed with bett'entone dis'cernmentjhowever; will :be able to detect suchto'nes as thirds', minor thirds; fifths, augmented fifths, ninths and; of course; octaves. Once-having'audibly recognized the correlation-between such tones and gripping force, it canbe" recognized that the operator can thereafter determine"with fairlygood accuracy various degrees of 'fdrceactually'being applied to'aremotely handled object.

In any event, practical use is made of the sound prodticnited States Patent" ice 2,847,663 Patented Aug. .12, r1958 21 mg apparatus to indicate when zero force is beingap plied, as by havingtthevariable pitch tone'then equalthe referencetone, and toindicate when, say, a maximum force is being applied, as by having thevariahle tone rise in pitch to an octave above the referencetone.

In remote handlingsystemsofthe character referred to, it has become necessary toat times changefrom one type of clamping device to another.- These clamping devicesor handsias they are-frequentlytermed are, therefore, detaehably. connected to a -forea-rm. Since certain manipulations must be understaken to switch from one mechanical hand toanother, it is essential-tmkn'ow when the release poi nt has beenreached; and his a desideratum of the invention-to indicate-in an audible manner the moment this: releaseisetfeeted; More specifically'; it is an object to indicate whentherrelease-has been accomplished in -such a way, thatthere r can never be any, confusionbetween force? tones and release" tones,v the invention envisagingtheemployment of reference tone pulses that are of shorter durationthan either saidforce and release tones; Stated somewhat differently, the tonesproduced asthehand is moved toward release are of courselower than the reference tone, and the tones generated asathe clamping forceis increased are always higher than the-reference tone. With the reference tones beingts horter, a fixed plateau or tone levelcansnev'er prevail by; which tone pulses below the true-reference mightbe confused with ithe true reference pulses in suchvla way as theoperator would "will not require'tha-t the voltage source be absolutely constant for proper functioning. In this regard, it is tobe noted thatit is the difference in pitch bet vveenthe reference and that which is ameasure of applied force which is instrumental in alldwingth operator todetermine to what extent any clamping action should be changed.

Still another object of the invention is to provide an exceedingly simple system and method for determining ona relative basis force differences, thereby permitting the-apparatus to be of comparatively low cost as far as its manufacture is concerned.

Other objects will' be in part 'obvious,l,and in part pointed out more -in-detail hereinafter.-

The invention accordingly consists in the features of construction, combination of eleinents and arrangement of parts which will be exemplified inathe construction hereafter set forth and the scope of the application which will be indicated in the-appended "claims.

In the drawings:

Figure 1 is "a perspective view of"a material handling unit with which my invention will find especial utility;

Fig.1 'is a detailed section through the forearm of the handling unit, this view illustratingia different mechanical form whi'ch the hand or grip rnayi-assu'me over that pictured generally ,in- F ..,-1 'togethei with certain associatedelectronic circuitryf or generating'the audio-tones; and

Figh 3 shows a hypothetical curve of pitch plotted against time, the attributes of this icurve 'having been selected so as to explain' certain features derivable from a-practicing ,of the invention.

While it is felt that a general understanding of a materialh andling unit, such as that more fully treated in the hereinbefo're mentioned Bergsland etal. application, and theattendant 'need forsubstit'uting one mechanical hand for another may be .hadfrom' 'the ensuing desciiptic'nyno ethe s's r sort should be made tosaidpergsland et aliapplication for suennetails that'mightnotbe' wholly clear to the reader. Actually, all of Fig. 1 and the mechanical portion of Fig. 2 have been taken directly from the Bergsland et al. application, being presented here largely for convenience in showing and claiming the instant invention.

With the above remarks in mind, attention is now directed to Fig. 1. In this. figure a framework is depicted. Surmounting the framework is certain power supplying superstructure not considered essential to the present invention. Relatively movable with respect to the framework isa shoulder unit 12 to which is pivotally connected an upper arm 14. The upper arm 14 in turn has pivotally attached to.it a forearm 16, and it is this forearm that carries what will be termed a hand or claw grip 18.

The construction of the hand 18 is susceptible to a variety of forms. Here the hand 18 includes a hook jaw member 20 movable longitudinally relative to an anvil jaw member 22 in the direction of the arrow 24. By reason of meshing teeth 26, the hand unit is also capable of rotation in the direction of the arrow 28.

The material handling apparatus, as already indicated, is intended for use where objects are to be moved in an atmosphere detrimental to human health. Accordingly, in order to render the apparatus versatile enough to handle items of various sizes and shapes, it becomes necessary to at times change from one type of hand to another. One such hand has already been given the reference numeral 18.

Another type of hand that may be substituted for the hand 18 is depicted in Fig. 2, this hand bearing the reference numeral 30. In this situation the hand resembles more a tong type of clamping device, comprising a pair of fiat jaw members 32 and 34 mounted for articulative movement in a transverse direction through the agency of sector gear elements 36 and a gear rack 38 meshed therewith. Integral with one end of the rack 38 is a flanged head 40 normally engaged by a pair of spring biased dog elements 42 provided with cam surfaces 44 by which the dog elements may be urged apart for the insertion of the head 40.

The dog elements 42 are pivotally carried by a rotatable and reciprocable bearing housing 46, said housing being recessed for the captive reception of the outer race of a ball bearing assembly 48. Via a threaded arrangement, an internally threaded sleeve is connected to the inner race of the bearing 48 for transmission of applied operating force to the rack 38. The end of the sleeve 50 opposite the bearing 48 is also internally threaded for the accommodation of one end of a screw member 52 having a power driven gear 54 circumscribed about and keyed to another portion thereof. The end of the screw member 52 remote from its threaded end is shouldered at 55 for abutment against a stack of spring washers 56. These concave-convex washers of course yield to an extent dependent upon the force transmitted to the clamping jaws 32 and 34, becoming progressively more planar with an increase in applied force.

By reason of a flange 58 integral with the screw member 52 any motion of said screw member is transferred proportionally to a pivotal arm 60. The. pivotal arm is utilized in actuating a potentiometer 64 set forth schematically in Fig. 2. Actually, reference to the arm 60 provides an apt introduction to-the circuitry with which the invention is primarily concerned.

Proceeding now with a description of exemplified circuitry by which the objects of the invention may be carried into practical being, it is to be noted that the potentiometer 64 is wiped by a brush 68 mounted on the lower end of the pivotal arm 60, and that a potentiometer 66 is wiped by a manually adjustable wiper 70. The two potentiometers 64 and 66 have their extremities connected together to a D. C. source (typically 20 volts), thus constituting a D C. bridge whose output, which is the D. C. signal fed "to the electronic indicator, is proclosing contacts 106.

portional to the grip force (or release force) being exerted by the hand or claw. The centering potentiometer 66 may be used to balance the bridge at a time when no grip force or release force is being exerted. Henceforth, increasing the grip force will effect an increase in the bridge output voltage up to ten volts having one polarity; conversely, increasing the release force will effect an increasing in the bridge output voltage up to ten volts of the opposite polarity.

The brushes 68, 70 are connected to opposite ends of a voltage divider 72. For low sensitivity the voltage divider is adjusted substantially as shown so that whatever voltage signal is produced by the potentiometer 64 will be divided so that only of such voltage is utilized. (As will presently become manifest, full swing, when divided down, is adjusted to give a tonal difference of two octaves.) When the full, undivided voltage of the potentiometer is used, then the sensitivity of the system is increased substantially twenty fold, permitting the handling of extremely frangible articles of egg shell thinness.

In accomplishing the above objective, a double throw single pole switch 74 is connected so that manipulation thereof will give the proper sensitivity range of operation. It is to be noted that the switch 74 is connected electrically to one grid 76 of a dual D. C. amplifier tube 78 such as a 12AT7 tube. The corresponding cathode 80 of this triode is connected to an audio centering adjustment potentiometer 82, which adjusts the fixed gridto-cathode voltage or bias; this pre-sets the D. C. amplifier at the center of its range of operation.

The plate 84 of the tube 78 is connected through its plate resistor to a plate supply source and to the grid 86 of the second triode (control triode) of the tube 78. The cathode 92 of the control triode is connected to a suitable positiveD. C. voltage point, and to one terminal of a voltage-responsive audio oscillator. The plate of this same triode is connected to one of a pair of contacts 106 on relay 98. When this relay is operated, contacts 106 close to connect the plate 90 through a suitable plate resistor 88 to the plate supply source.

The relay 98 has a coil 100 and an armature 102. The coil 100 is alternately energized and de-energized by the operation of a multivibrator 104 in a cyclic fashion. During the period when the coil is de-energized (typically one-third second), contacts 96 are closed, connecting a fixed resistor 108 in series with the plate resistor 88. Resistor 108 has a value identical to the plate-to-cathode resistance of the control triode when at the center of its range of operation. When the relay coil 100 is energized, the armature 102 is retracted, opening contacts 96 and This removes the resistor 108 from the circuit in series with resistor 88 and replaces it with the plate-to-cathode resistance of the control triode. The lower end of the resistor 88 is connected to one of the contacts 106, one of the contacts 96 and to the second terminal of the audio oscillator; in this manner, the alternations of the multivibrator 104 cause the relay 98 to present to the input terminal of the audio oscillator D. C. voltages which alternate between a fixed value ob tained when the relay is de-energized and a variable value obtained when the relay is energized.

From the typical voltage values shown in parenthesis in various points in the diagram of Fig. 2, it may be seen that cathode 80 operates at a typical potential of +2 v., cathode 92 at +110 v., grid 76 in the range of +5 v. to -.5 v., amplified in the input triode so that plate 84 operates in the range +100 v. to +110 v. (also the range of grid 86), amplified in the control triode so that plate 90 operates over the range +150 v. to +250 v. (typical). This results in the plate 90 being always positive with respect to its cathode 92 in a typical range of 40 v. to v. This is the variable voltage impressed on the input of the audio oscillator when the relay 98 is energized.

mamas Asexplained above the function of the multivibrator 104 is'to energize the relay 98: This is donein a repetitive manner, the circuit constants of the multivibrator being selected so that the period of energization of thecoil 100 is diiferent from its period of de-energizationn Suggestively, the period of energization might be one second and the period of de-energization might be /asecond. Thus the resistor 108 is placed in the oscillator circuit less time than is the control triode, and in this way the-desired time ratiois obtained between the reference and variable pitch tones.

By initially. setting the audio centering potentiometer 82, themid-point of the tonal range, through which the variable pitch extends, maybe obtained. The over-all rangeof theaudio oscillator 94 should preferably be two octaves, The mid-pointof this range should correspond in frequency level with the reference tone and should indicate when no clamping force exists as far as the jaws 32 and 34 are concerned. One octave above this frequencyis selected so as to representaudibly themaximum amount of gripping force to which the jaws 32'and 34 should be subjected. For instance, such a maximum might be governed by the frangibility of the article to be handled or it might be dependent upon the degree of clamping format which the driving slipclutch (not described) starts to slip. As for makingit possible for the operator to recognize when the jaws 32 and 34 have been opened to the hand-release point, a-low' pitch tone, i. e., a pitch well below the reference pitch'is selected, a tone an octavebelow being easily discernible and therefore recommended.

- The'above may be succinctly presented iii-a visual manner by reference to Fig. 3 where there'app'ears a curve generally indicated by the reference numeral 114. As can-be seen frorn this figure the curve is iplottedwith pitch orfrequency as the ordinate and time as the abscissa. The curve 'is rather hypothetical inasmuch asiinactual practice the various promontories will not deviate so abruptly from those .next adjacent.

Assuming'that there is no gripping force applied to the jaws'32 and 34, then the variable pitch. willequal the reference pitch and that portion of the curve will appear as a straight horizontal line 116. Howevenwhen the jaws 32,and 34 are moved underthesupervisory control of the operator in a direction to apply pressure against an object being held, the variable pitch starts toincrease in accordance with the force exertedv as indicated by the numeral 118. These pulses, periods,or promontoriesas they might be loosely termedhere increase until an octave level above the reference pitch is reached, such a level being indicated by the numeral 120. Proceeding with the description of curve 114,- we will now assume that the clamping force is moderated, starting with the pulse 122 and returning to zero at 124.

Having returned to the zero forceor referencepoint, for :the sake of illustration it will now bepresurnedithat the operator is desirous of releasing the hand..39 for substitution with the hand 18 (Fig. 1): To dothis the jaw members 32 and 34 are actuated to a wide open position causing the cam surfaces 44 of the dog elements 42 to strike the cam face of a collar 126 so as to urge the dog elements apart. There is also a locking ring 128 that must be pushed in by forcing the forearm 14 down against cantilever arms 130 and 132 affixed to the framework 10. Such action is instrumental in freeing locking balls 134 from a drive sleeve 136 on which the jaws 32 and 34 are indirectly supported.

All of the preceding detail is set forth fully in the aforenoted Bergsland et al. application. The information needed at this point, however, is that the flange 58 is being moved during this period in a direction opposite to that in which it is moved when a clamping force is being applied via the screw member 52. Such a procedure results in the potentiometer 64 applying a different voltageitocthe grid 76rof thetamplifier'tube 78c, Through the medium of the control triodetof .tube -78 .aidiiferent con trol signal is impressed on'the oscillator 94with the'result that the oscillator emits a signal having a'progressively lower pitch, proceeding from a frequency locus 138"on theicurve 114 down'to the release point 140, preferably an octave below the: reference level. and two octaves below the maximum forcepitch earlier designatedby the numeral 130.-

In other'words, the pitch representedby the numeral 140 is indicative of'thecondition in' which the hand 30 has been readied for depression'of the locking ring 128,

thereby to release the tong type band 18 so as to permit replacement thereof with the hook type hand- 18.

While a number of audio frequencies might be utilized in the effectuation of the reference tone and'th'e maximum and minimum pitch levels represented by-the numerals 120and 140, respectively, nonetheless a frequency of approximately cycles per second 'may be employed-as the reference pitch, thus insuch an instance causing the highest pitch to be 360 cyclesper'second and the lowest pitch to'be'90 cycles persec'ond-(i. e., an octave 'abo've and an octave below).

Fromth'eforegoing description it is believed apparent that the instant invention has dealtwith'a 'method and apparatus by which anuntrained 'individual will quickly grasp the rudiments of-operation. With practice, especially where persons are involved who possess a'tone trained ear, exceptional results can be expected as far as'precise graduations of applied force are concerned. However; for most operations, because the operators ears are 'continually subjected tothe reference tone, it iseasy to discern when the applied force is beingmodified and'to what relative extent; It is with the musically trained ear that specific magnitudes of force canb e differentiated, as by noting thirds, minor thirds, fifths, augmented fifths, andninths. In som'e cases those frequencies in between can be recognized, depending largelyupon the' sensitivity of the operators ear. It is to be further appreciated that the invention is-quite replete, taking into consideration the fact that the mechanical hands themselves must at times be 'changed and affording a facile way for determining when the m'aterialhandling apparatus has been properly conditioned for suchchange.

As many changes could be made'in the above con struction' and many apparently widely diif'erent embodiments of this invention could be made without departing from the scope thereof, itis intended thatall matter contained in the above description or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that thelanguage used in the following claims is intended to cover all of the generic and specific features of the invention herein described and allstatements of the scope of" the invention which,

as. aumatter of llanguage, might be said to fall therebe-.

'worka clamping members, i an audio grip force indicator comprising sound producing means, means for producing a reference tone from saidsound means having a given pitch, and means operatively associated with one of said clamping members for producing a tone from said sound means having a pitch variable in accordance with the force exerted by said clamping members against an object held therebetween, and means for repeatedly alternating said reference tone, with said variable tone in a cyclic manner.

2. In combination with a pair of relatively movable work clamping members, an audio grip force indicator comprising sound producing means, means for producing a reference tone from said sound means having a given pitch, means operatively associated with one of said clamping members for producing a pitch variable in ac- 7 cordance with the force exerted by said clamping members against an object held therebetween, and means for adjusting the pitch of said variable tone to that of said reference tone when no force is exerted by said clamping members.

3. In combination, an arm member, a hand mechanism including a pair of relatively movable work clamping members, means releasably attaching said hand mechanism to said arm, and audible means for indicating when said attaching means is in a releasing position including means for producing a reference tone and a signal tone diifering from said reference tone by a predetermined pitch differential when said attaching means has reached its release position.

4. In combination, an arm member, a hand mechanism including a pair of relatively movable work clamping members, means releasably attaching said hand mechanism to said arm, said means releasing said hand mechanism at a preferred degree of separation of said clamping members, and audible means for indicating when said clamping members have reached said preferred degree of separation thereby signifying when said hand mechanism has been conditioned for release, said audible means pro ducing a predetermined pitch differential when said hand mechanism has been conditioned for release.

5. In combination, an arm member, a hand mechanism including a pair of relatively movable work clamping members, means releasably attaching said hand mechanism to said arm, said means releasing said hand mechanism at a preferred degree of separation of said clamping members, an audio grip force indicator comprising sound producing means, means for producing-a reference tone from said sound means having a given pitch, and means actuated by one of said clamping members for producing a pitch variable in one direction in accordance with the force exerted by said clamping members against an object held therebetween and variable in an opposite direction to a selected pitch for audibly indicating when said clamping members have reached a preferred degree of separation thereby signifying when said mechanism has been conditioned for release.

6. In combination, a clamping device including a pair of relatively movable work clamping members, means for actuating said clamping members, a potentiometer, means connected to said actuating means for positioning said potentiometer, amplifying means connected to said potentiometer, a control tube, a resistance, an audio oscillator, switch means for alternatively coupling either said control tube or resistance to said amplifying means to produce a tone having a pitch variable in accordance with the force exerted by said actuating means against said clamping members and a reference tone having a given pitch, respectively, and speaker means connected to said oscillator.

7. The combination set forth in claim 6 including a voltage divider between said potentiometer and said amplifying'means, and switch means in circuit with said divider and amplifier means for changing the magnitude of the signal from said potentiometer.

8. The combination set forth in claim 6 including means for holding said clamping device, means for releasing said clamping device from said holding means, said amplifying means being capable of producing said variable tone so that it has a range of pitch extending approximately an octave above said reference tone and an octave below said reference tone, said lower octave indicating when said releasing means is in a release position.

9. Apparatus for indicating audibly the gripping force applied to a pair of relatively movable clamping mem bers comprising mean for producing a reference tone having a relatively constant pitch for a given period, means for producing another tone for a different period having a pitch variable in accordance with the force exerted by said clamping members against an object held therebetween, and means for alternating said constant pitch tone and said variable pitch tone with each other in a repetitive fashion.

10. Apparatus for indicating audibly the gripping force applied to a pair of relatively movable clamping members comprising means for producing a reference tone having a relatively constant pitch for a given period, and means for producing another tone having a pitch variable in accordance with the force exerted by said clamping members against an object held therebetween for a period differing in time from said given period.

11. Apparatus for indicating audibly the gripping force applied to a pair of relatively movable clamping members comprising means for alternately producing a reference tone having a relatively constant pitch for one period of time and means for producing another tone having a pitch variable in accordance with the force exerted by said clamping members against an object held therebetween for a different period of time.

12. Apparatus for indicating audibly the gripping force applied to the jaws of a clamping mechanism and the point at which said clamping mechanism is released from its holder comprising means for producing a reference tone having a relatively constant pitch for one period of time, and means for producing another tone for a different period of time variable in one direction in accordance with the force exerted by the jaws of said clamping mechanism and in :an opposite direction to indicate when the clamping mechanism has been released.

13. The apparatus set forth in claim 12 in which the variable tone is variable to an octave above the reference References Cited in the file of this patent UNITED STATES PATENTS 2,519,015 Bensen Aug. 15, 1950 2,576,017 Jeffrey et al Nov. 20, 1951 2,605,330 Progress July 29, 1952 2,670,626 Hall Mar. 2, 1954 

